1. Field of the Invention
This invention relates to digital cameras and, more particularly, to a digital camera which creates an image signal having a desired zoom magnification.
2. Description of the Prior Art
In the conventional digital cameras of this kind, where creating a zoom image signal having a desired zoom magnification from an image signal due to picture taking, the image signal has been once stored into a field memory. Thereafter the image signal has been subjected to a zooming process by using a line memory, adder, multiplier and so on.
In such conventional arts, however, the zooming process has required such circuits as a field memory, line memory, adder, multiplier, etc., thus resulting in a problem of complicated circuit configuration.
Therefore, it is a primary object of the present invention to provide a digital camera which is capable of creating an image signal having a desired zoom magnification through a simplified circuit configuration.
According to the present invention, a digital camera, comprising: a picture taking means for taking a picture of a subject and outputting a first image signal having a first number of pixels; a creating means for creating a second image signal having a second number of pixels smaller than said first number of pixels by extracting a predetermined pixel signal from said first image signal; a setting means for setting a zoom magnification; and a change means for changing a position of extracting said image signal depending upon said zoom magnification.
If a first image signal having a first numbers of pixels is outputted from the picture taking means, the creating means extracts a predetermined pixel signal from the first image signal to create a second image signal having a second number of pixels. Here, the position of extracting the image signal is changed depending upon a zoom magnification set by the setting means.
According to the present invention, a second image signal with a desired zoom magnification can be obtained by changing the position of extracting the pixel signal from the first image signal. Thus, the circuit configuration can be simplified.
In a certain aspect of the present invention, the creating means includes a thin-out means and a cut-out means. The thin-out means subject the first image signal to thinning out into a second image signal. The cut-out means cuts out a predetermined portion of the first image signal into a second image signal. Due to this, the change means activates selectively the thin-out means and the cut-out means depending upon a zoom magnification.
In a certain embodiment of the present invention, the activating means activates the thin-out means when a 1-times zoom magnification is set, and the cut out means when a 2-times zoom magnification is set.
In another aspect of the present invention, the thin-out means includes a plurality of registers and an enabling means. The registers cause the first image signal to shift by a first predetermined amount a time, and the enabling means intermittently enables these registers.
In a certain embodiment of the present invention, the first image signal includes a signal, a U signal and a V signal which are different in data amount one another, and the registers includes a plurality of first registers and a plurality of second registers. The Y signal is shifted by 1 pixel a time by the first registers, whereas the U signal and the V signal are shifted by 1 pixel a time and alternately by the second registers. Also, the enabling means includes a first enabling means and a second enabling means. The first enabling means intermittently enables the first registers for a 1-pixel period a time, while the second enabling means intermittently enables the second registers for a 2-pixel period a time.
In other aspects of the present invention, the cut-out means cuts a second image signal in the following manner. That is, a request output means outputs a request to read the first image signal held in the buffer. A gate means applies gating to some read request. A read means responds to the read request outputted from the gate means and reads the first image signal out of the buffer. Incidentally, the request output means output the read request each time the first image signal is written in a second predetermined amount to the buffer.